Metal-plastic composite racquet

ABSTRACT

A game racquet comprising a composite metal and plastic frame having a stringing section and a handle, the composite frame formed from an extruded metal channel member surrounding and substantially enclosing an extruded plastic core member, the extruded metal and plastic core member being bonded together to form a unitary metal-plastic composite frame, .Iadd.wherein the horizontal neutral axis of the core member is closely aligned with the horizontal neutral axis of the metal channel member .Iaddend.and a bumper strip covering the outer surface of the composite frame, the bumper strip having a central groove to receive and protect the stringing.

BACKGROUND OF THE INVENTION

This invention relates to a new and unique game racquet for use inplaying racquetball, squash or similar games in which a compositeextruded metal and plastic frame is employed to secure a racquet havingthe desired balance and flexibility for better ball control but withsufficient durability to withstand extensive use in either recreationalor tournament play without objectional deformation.

Laminated wood and extruded metal frames of aluminum, aluminum alloys,and stainless steel, have been previously used in the manufacture ofracquets but such frames all have limitations which resist universalacceptance, and extensive experimentation has been conducted in aneffort to secure a racquet incorporating all the desired characteristicsof previously designed frames without increasing the cost of manufactureover the procedures customarily employed.

In view of inherent strength, a tubular or channel steel frame structureprovides a logical choice for racquets of the type in question but havebeen found to be objectionable because of excessive flexibility orexcessive weight. Extruded frames of aluminum or aluminum alloys possessthe desired rigidity, but as noted in the prior art, such as the patentto Vaughan et al., U.S. Pat. No. 3,899,172, of Aug. 12, 1975, suchframes have a tendency to deform in use. However, bending strength isnot the characteristic that determines durability. The ability of theframe to absorb energy without yielding is the important characteristicbecause the racquet does not transmit a force to the ball, but rather ittransmits energy that has been developed by the player's arm and storedin the racquet. My composite frame has excellent energy storage capacityas compared with conventional tubular aluminum frames.

Extruded metal frames also have been found to be objectional in thatstring wear may be excessive at the point of contact between the stringsand the metal edges of the stringing holes. The strings are subject toexcessive wear resulting from the friction as the ball strikes thestrings, causing the strings to fail at that point.

Modifying the cross-section design of the metal frame in an effort toovercome this objection presents a problem. Increasing the thickness ofthe web of the metal frame member without increasing the weight, reducesthe strength of the frame and increases the tendency to breakage.Present designs represent a compromise between springing action anddurability, dictated in part at least, by costs of manufacture.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a game racquetincorporating as far as possible all the desired features of previousdesigns but eliminating the characteristics which have been found to beobjectional.

I have found that my novel construction and design of a game racquet inwhich the frame comprises a composite extruded metal channel membersubstantially encasing an extruded plastic core, the plastic extrudedcore being affixed or bonded to the metal channel member by means of asuitable adhesive, results in a composite metal-plastic frame ofimproved strength and durability but incorporating the desired degree offlexibility. In addition, a soft plastic suspension is provided for thestrings and the necessity for grommets or rivets is eliminated.

The advantages of my new design will be apparent to those skilled in theart from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the racquet made in accordance with thepresent invention.

FIG. 2 is a cross sectional view taken along lines II--II, of FIG. 1.

FIG. 3 is an exploded view, in prospective, showing construction detailsand the manner in which the composite frame is assembled and attached tothe handle.

FIGS. 4, 5, 6 and 7, are cross sectional views of modifications of themetal and plastic extrusions which may be used in fabricating the framemember of the racquet in accordance with the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, the game racquet described herein, comprises acomposite frame, including an extruded metal channel member 1, such asaluminum, substantially surrounding and encasing an extruded plasticcore 2, as shown in FIG. 2, formed into a generally oval shape to definea stringing surface, a plastic bumper strip 3, having a channel 3a, toprotect the stringing, and a throat piece 4, secured to the metalchannel member 1, by means of screws 6, to reinforce and impart rigidityto the composite frame. The throat piece 4, may be solid or, if desired,may have an opening 5, therein of any desired configuration, but oflimited size, so as not to materially weaken the same.

The metal frame member, a cross-section of which is shown in FIG. 2, isa custom extrusion in the shape of an "inverted U", designed to providethe proper bending moment of inertia in the x and y axes, while havingthe proper weight per length of frame and the proper height and widthfor reasonable appearance of the finished article.

The plastic core 2, is also a custom extrusion having the shape of an"inverted T," which fits within and is affixed to the metal channelmember 1, forming a composite bonded metal-plastic frame. The plasticcore member serves to reinforce and impart a certain degree of rigidityto the metal channel member.

The plastic core member 2, and plastic bumper strip 3, are preferably ofABS, although any extrudable plastic with similar rigidity and highimpact strength, such as nylon, rigid PVC, or polycarbonate, isacceptable.

If it is desired to weight the head of the racquet to affect balance,weight and feel, small diameter lengths of a dense material, such aslead 8, as shown in FIG. 2, may be bonded to the metal section of theframe with a flexible adhesive, such as epoxy, although any adhesivewith reasonable flexibility and bond strength between the metal frameand the weighting material may be used. This feature of the frame designis of significant advantage since the amount of weight necessary toachieve desired balance may be readily varied and the weight is totallyobscured in the completed racquet.

In the manufacture of my racquet, the metal channel extrusion 1, and theplastic core extrusion 2, are cut to length and the plastic extrusionbonded into the metal channel member with an adhesive, such as epoxy,and the adhesive allowed to cure to form a composite metal-plasticframe. While epoxy is normally used as the bonding agent, any adhesivewith the requisite flexibility and bonding strength between the metalchannel member and the plastic core, may be used.

The length of composite frame is then formed around a mandrel togenerate the proper racquet frame shape. The plastic bumper extrusion 3,is bonded to the formed composite frame with an adhesive, such as epoxy,or any adhesive of comparable flexibility and bond strength. The plasticbumper strip 3, cannot be bonded before forming the frame because thehorizontal neutral axis of the plastic bumper extrusion is displacedconsiderably from the horizontal neutral axis of the metal extrusion andthe adhesive bond between the two would be placed under an excessivelyhigh sheer loading when forming the composite frame.

Holes are then drilled into the slot of the plastic bumper strip 3,indicated at 3b, FIG. 2, through the formed composite frame toaccomodate racquet stringing. Additionally, screw holes are provided inthe throat area of the formed composite frame to receive the screws 6,to allow attachment of the throat piece 4.

The throat piece may be of molded plastic and can be formed from epoxy,fiber glass reinforced epoxy, nylon, fiber glass reinforced nylon,polycarbonate, or any other plastic or fiber glass reinforced plastichaving at least moderate rigidity and high impact tensile strength. Thethroat piece has holes drilled or molded in place that coincide withholes in the formed composite frame to accommodate stringing and receivethe screws 6. The strength of attachment of the throat piece to theframe can be improved by applying an adhesive between the throat pieceand the composite frame before inserting the screws, as described above.

The handle for the racquet can be formed in several ways. As shown inFIG. 3, two corresponding shaped wooden members, 10 and 11, having"U-Shaped" channel sections, 12, and 13, respectively, adapted toreceive the lower end of the composite frame, are adhesively bondedtogether and allowed to cure. Pins 14, and 15, pass through holes 16,and 17, in handle member 10. Before securing the two handle sectionstogether, a thong 18, is looped over the pin 15, to provide a convenientmeans to hang the racquet when it is not in use. The composite frame isthen inserted in the handle and adhesively bonded thereto with epoxy orcomparable adhesive. Before inserting the lower portion of the compositeframe into the handle, the frame is drilled to receive the pin 14. Whileonly one pin has been shown in the drawing for this purpose, additionalpins to secure more rigid attachment may be used, if desired. A leathergrip may then be wrapped around the handle and the racquet strung withnylon string.

In addition to the construction shown in FIG. 3, the handle can bemolded in a lightweight foamed plastic for reduced costs in largequantities.

The metallic frame with the plastic "Inverted T" extrusion bonded inplace results in a composite frame having unique structural propertiesthat the metal and plastic extrusions by themselves do not possess. Thebending rigidity of the composite frame is somewhat higher than that ofthe metal extrusion while the torsional rigidity of the composite frameis higher than that of the aluminum extrusion. Additionally, thecomposite is more stable during forming and can be bent to small radiuscurves (less than 5 times cross section height) without visibledistortion. However, the metal extrusion distorts drastically whenformed to such curves. An important feature of my frame design thatmakes forming more practical is that the horizontal neutral axis of theplastic "Inverted T" extrusion is closely aligned with the horizontalneutral axis of the metal extrusion. This reduces the shear loading inthe adhesive bond between the plastic extrusion and the metal extrusionto a minimum.

Tests with my new racquet design show that is has many desirablefeatures. The composite frame is highly flexible which allows the ballto remain on the strings for a greater length of time, producing betterball control for the player. Currently marketed fiberglass racquets havethis same feature but are not very durable. The herein described racquetis very durable and has outlasted one of the more durable metal frameracquets in laboratory tests.

Material and labor costs per racquet for the herein described design arecomparable to currently marketed metal frame racquets while toolingcosts for my racquet are significantly lower than for fiberglassracquets.

The cross sectional shapes for both the metal and plastic extrusions maybe varied, a few examples being shown in FIGS. 4, 5, 6 and 7. Thesemodifications, however, all have the same basic structure in that anextruded metal channel member substantially surrounds and is bonded toan extruded plastic core to form a unitary composite frame. In eachinstance, as shown in these Figures, and also in FIG. 2, the shape ofthe plastic extrusion is such as to leave a channel .Iadd.9.Iaddend.between the metal and plastic within which small diameterlengths .Iadd.8 .Iaddend.of a weighting material, such as lead, may beinserted to provide the desired balance and feel, as explained inconnection with the description of FIG. 2.

In the form shown in FIGS. .[.5.]. .Iadd.4.Iaddend., and .[.6.]..Iadd.5.Iaddend., as well as in FIG. 2, the plastic extrusion is in theform of an "Inverted T," in FIG. .[.7.]. .Iadd.6.Iaddend., the extrusionis in the form of an "H", while FIG. .[.8.]. .Iadd.7 .Iaddend.reveals amodification in which a rectangular or substantially square extrusion isemployed.

The plastic bumper strip extrusion, likewise, may take a number ofdifferent forms, as illustrated in FIG. 2, and FIGS. 5 through 7. Ineach instance, however, the strip is provided on its exposed edge with acentral channel 3a, within which the strings are recessed and protectedfrom wear and abrasion.

The plastic bumper strip also serves several other purposes since itreduces the shock transmitted to the racquet frame when struck against afloor or wall. Since the bumper strip is a structural part of theracquet it increases the bending and torsional stiffness and strength ofthe frame and acts as a smooth surface for the strings without theaddition of metal or plastic grommets.

The racquet constructed in accordance with the above description isattractive, sturdy, and because of the simple cross sections of theextrusions and lack of large molded sections, only inexpensive toolingis required for production.

This invention has been described with reference to the preferredembodiments thereof but it will be understood that variations andchanges, obvious to those skilled in the art, may be made within thespirit and scope of the appended claims.

I claim:
 1. In a game racquet;a composite metal and plastic framedefining a stringing section and a handle; the composite framecomprising a unitary substantially rectangular extruded metal channelmember having in cross-section, an "M" configuration, the outer sidewalls of which are substantially parallel, said metal channel memberhaving a closed top outer section and a partially closed bottom innersection, the lower edges of the side walls of the metal channel memberhaving an integral continuous reinforcing and thickening rib along theinner surfaces thereof partially closing said bottom section of themetal channel member and imparting rigidity to the composite frame; anextruded plastic core member mounted within and bonded to the lowerinside surface and the inner surface of the side wall reinforcing ribsof the metal channel member to form a unitary frame, the outer surfaceof the plastic core being substantially encased by the metal channelmember and so dimensioned as to leave a space between the side walls ofthe metal channel member and the plastic core for the reception of aweighting material; a reinforcing throat piece attached to and impartingrigidity to the frame; and a plastic bumper strip covering the outersurface of the metallic frame member, stringing holes passing throughthe bumper strip and the composite frame, the plastic bumper striphaving a central groove to receive and protect the stringing fromabrasion.
 2. A game racquet as defined in claim 1, in which the uppersurface of the extruded metal channel member is provided with a centralgroove, the plastic bumper strip being partially recessed in saidgroove.
 3. A game racquet as defined in claim 1, in which the extrudedplastic core member is in the form of an "Inverted T".
 4. A game racquetas defined in claim 1, in which the extruded plastic core member is inthe form of an "H".
 5. A game racquet as defined in claim 1, in whichthe extruded plastic core member is bonded to the extruded metal channelmember by means of an adhesive.
 6. A game racquet as defined in claim 1,in which the extruded plastic core member is affixed to the extrudedmetal channel member with an epoxy adhesive.
 7. A game racquet asdefined in claim 1, in which a weighting material of lead is inserted inthe channel between the extruded metal channel member and the extrudedplastic core. .Iadd.
 8. In a game racquet, a composite metal and plasticframe formed intermediate its ends into a head defining a stringingsection and having its opposite ends adjacently side by side fordefining a handle section, said frame comprising a preformed metalstrip, a solid preformed synthetic plastic core member, and an outerpreformed strip of synthetic plastic, said core member and said metalstrip being substantially coextensive in length, said metal strip beingof generally U-shape in cross section to define an inwardly open channelhaving an outer wall and inwardly extending side walls, the lower edgesof said side walls each having an integral continuous reinforcing andthickening rib along the inner surfaces thereof partially closing thechannel and imparting rigidity to the composite frame, said core memberbeing disposed wholly within said channel and extending between andbeing surface bonded directly to the inner sides of said ribs and saidouter strip being surface bonded directly upon the outer side of saidouter wall, said outer plastic strip extending laterally to protectivelycover the outer surface of said channel outer wall and extendinglongitudinally around the end of said stringing section opposite thehandle section, whereby said bonded strips mutually contribute toprovide a laminated structure of increased rigidity and energy absorbingcharacteristics, and means providing in the stringing section a seriesof aligned stringing holes extending through said core member and saidstrips. .Iaddend..Iadd.
 9. In the game racquet defined in claim 8, athroat element of moderately rigid synthetic plastic mounted on theframe to define the inner end of said stringing section. .Iaddend..Iadd.10. In the game racquet defined in claim 8, there being a continuousnarrow external groove in said outer wall of the channel and said outerplastic strip being so constructed and arranged as to fill said grooveand extend over the adjacent outer surfaces of said outer wall..Iaddend..Iadd.
 11. In the game racquet defined in claim 10, said outerplastic strip being formed with an external groove adapted to receiveand protect stringing in said stringing section. .Iaddend..Iadd.
 12. Inthe game racquet defined in claim 8, said core member being an extrudedplastic strip of uniform cross section, and said outer strip being anextruded plastic strip. .Iaddend. .Iadd.
 13. In a game racquet, acomposite metal and plastic frame defining a stringing section and ahandle, the composite frame comprising a unitary substantiallyrectangular extruded metal channel member, said metal channel memberopening inwardly and having a bottom wall and inwardly extending sidewalls, integral continuous thickening and reinforcing ribs extendingalong the inner ends of said side walls partially closing said channeland imparting rigidity to the composite frame, a solid plastic coremember of substantially the same length as said channel substantiallywholly mounted within and surface bonded to the inner surfaces of theside wall reinforcing ribs of the metal channel member, and a continuousplastic bumper strip bonded upon the outer surface of the channel bottomover at least the end of said stringing section opposite said handle,whereby said bonded channel member, core member and bumper stripmutually contribute to provide a laminated structure of increasedrigidity and energy absorbing characteristics there being alignedstringing holes passing through the strips and the channel bottom, andthe plastic bumper strip having its stringing holes opening into acentral outwardly open groove to receive and protect the stringing fromabrasion. .Iaddend. .Iadd.14. A game racquet defined in claim 13, inwhich the extruded core member is in the form of an "Inverted T". .Iadd.15. In a game racquet, a composite metal and plastic frame formedintermediate its ends into a head defining a stringing section andhaving its opposite ends adjacently side by side for defining a handlesection, said frame comprising an extruded metal strip and a preformedsubstantially coextensive synthetic plastic core member, said metalstrip being of a cross section to define a channel having a bottom walland side walls, the lower edges of said side walls each having anintegral continuous reinforcing and thickening rib along the innersurfaces thereof partially closing the channel and imparting rigidity tothe composite frame, said core member being disposed substantiallywithin said channel and extending between and being adhesively bondeddirectly to inner surfaces of said ribs, said core member being bondedto said metal strip prior to forming the composite metal-plastic todefine said stringing section, and the horizontal neutral axis of saidplastic core member being closely aligned with the horizontal neutralaxis of said metal strip to minimize shear loading in the adhesive bondbetween the plastic core member and the metal strip, whereby said metalchannel and plastic core member mutually contribute to provide alaminated frame structure of increased rigidity and energy absorbingcharacteristics, and means providing in the stringing section a seriesof aligned stringing holes extending through said core member and saidmetal strip. .Iaddend..Iadd.
 16. In a game racquet, a composite metaland plastic frame formed intermediate its ends into a head defining astringing section and having its opposite ends adjacently side by sidefor defining a handle section, said frame comprising an extruded metalstrip and a preformed substantially coextensive synthetic plastic coremember, said metal strip being of a cross section to define a channelhaving a bottom wall and side walls, said core member being disposedsubstantially within said channel and extending between and beingadhesively bonded directly to the inner sides of said side walls and tothe inner side of said bottom wall and said core member being of suchshape as to define a closed channel between the plastic core member andsaid metal strip, a bumper strip of synthetic plastic materialprotectively overlying the outer surface of said channel bottom wall andextending around the end of the stringing section opposite the handlesection, and means providing in the stringing section a series ofaligned stringing holes extending through said core member, said bumperstrip and said metal strip. .Iaddend. .Iadd.
 17. In a game racquet, acomposite metal and plastic frame formed intermediate its ends into ahead defining a stringing section and having its opposite endsadjacently side by side for defining a handle section, said framecomprising an extruded metal strip and a preformed substantiallycoextensive synthetic plastic core member, said metal strip being of across section to define a channel having a bottom wall and side walls,the lower edges of said side walls each having an integral continuousreinforcing and thickening rib along the inner surfaces thereofpartially closing the channel and imparting rigidity to the compositeframe, said core member being disposed substantially within said channeland extending between and being adhesively bonded directly to the innersides of said ribs whereby to close the channel and provide a laminatedstructure of increased rigidity and energy absorbing characteristics, abumper strip of synthetic plastic material protectively overlying theouter surface of said channel bottom wall and extending around the endof the stringing section opposite the handle section, and meansproviding in the stringing section a series of aligned stringing holesextending through said core member said bumper strip and said metalstrip. .Iaddend..Iadd.
 18. In the game racquet defined in claim 17, saidcore member being solid and of inverted T-shape with the stem of the Textending toward said bottom wall. .Iaddend..Iadd.
 19. In a gameracquet, a composite metal and plastic frame formed intermediate itsends into a head defining a stringing section and having its oppositeends adjacently side by side for defining a handle section, said framecomprising a preformed metal strip and a solid preformed substantiallycoextensive synthetic plastic core member, said metal strip being of across section to define a channel having a bottom wall and side walls,the lower edges of said side walls each having an integral continuousreinforcing and thickening rib along the inner surfaces thereofpartially closing the channel and imparting rigidity to the compositeframe, said core member being disposed substantially within said channeland extending between and being surface bonded directly to the innersides of said ribs to define a closed channel, a bumper strip of solidsynthetic plastic material protectively overlying and bonded upon theouter surface of said channel bottom wall and extending around the endof the stringing section opposite the handle section, whereby saidbonded core member and strips mutually contribute to provide a laminatedstructure of increased rigidity and energy absorption characteristicsand means providing in the stringing section a series of alignedstringing holes extending through said core member, said bumper stripand said metal strip. .Iaddend.